FIG. 4 is an arrangement view showing an outline of the conventional uniterruptible electric power supply.
In the view, reference numeral 1 is an AC electric power supply, reference numeral 2 is a condenser connected in parallel with the AC electric power supply 1, reference numeral 3 is an inrush electric current inhibiting resistor for inhibiting an inrush electric current, reference numeral 4 is a switch connected in parallel with the inrush electric current inhibiting resistor 3, reference numeral 5 is an AC-electric-power-supply/battery changeover switch for changing over between the AC electric power supply and the battery, and reference numeral 6 is a reactor for forming a filter together with the condenser 2.
One end of the AC electric power supply 1 and one end of the AC output are connected with each other by a common line, and a connecting point of the first condenser 14 and the second condenser 15, which are connected with each other in series, is connected with the common line. The other end of the AC electric power supply 1 is connected with the inrush electric current inhibiting resistor 3 and the switch 4 which is connected in parallel with the inrush electric current inhibiting resistor 3. The contact “a” of the AC-electric-power-supply/battery changeover switch 5 is connected with the inrush electric current inhibiting resistor 3 and the switch 4, which is connected in parallel with the inrush electric current inhibiting resistor 3, when the AC electric power supply is turned on. The contact “b” is connected with the battery operation switch 27 described later when the battery is turned on. The contact “c” is connected with the reactor 6.
Reference numerals 7, 8, 9 and 10 are diodes composing a diode bridge, and reference numeral 11 is a first semiconductor switch connected with this diode bridge in parallel. The diode bridge, which is composed of the diodes 7, 8, 9 and 10, and the first semiconductor switch 11, which is connected with the diode bridge in parallel, compose a converter section and connect between one end of the reactor 6 and the common line.
Reference numeral 12 is a first diode for preventing a back current, reference numeral 13 is a second diode for preventing a back current, reference numeral 14 is a first condenser connected between the P-voltage line and the common line, and reference numeral 15 is a second condenser connected between the common line and the N-voltage line.
Reference numeral 16 is a first semiconductor switch in the inverter section, reference numeral 17 is a diode connected in reverse parallel with the semiconductor switch 16, reference numeral 18 is a second semiconductor switch in the inverter section, and reference numeral 19 is a diode connected in reverse parallel with the semiconductor switch 18. The semiconductor switch 16, diode 17, semiconductor switch 18 and diode 19 compose an inverter section for converting DC electric power, which is sent from the DC electric power supply including the first condenser 14 and the second condenser 15, into AC electric power.
Reference numeral 20 is a filter composed of the reactor and condenser, and reference numeral 21 is a load.
Reference numeral 22 is a first semiconductor switch of the balance section, reference 23 is a diode connected in reverse parallel with the semiconductor switch 22, reference numeral 24 is a second semiconductor switch of the balance section, reference numeral 25 is a diode connected in reverse parallel with the semiconductor switch 24, and reference numeral 26 is a reactor of the balance section.
The first semiconductor switch 22 of the balance section, one end (the collector side in the drawing) of which is connected with P-voltage line and the other end (the emitter side in the drawing) of which is connected with one end (the collector side in the drawing) of the second semiconductor switch 24 of the balance section and also connected with the reactor 26 of the balance section, the second semiconductor switch 24 of the balance section, one end. (the collector side in the drawing) of which is connected with the other end of the first semiconductor switch 22 of the balance section and also connected with the reactor 26 of the balance section and the other end (the emitter side in the drawing) of which is connected with N-voltage line, the back current preventing diode 23, the cathode side of which is connected with one end (collector side in the drawing) of the first semiconductor switch 22 of the balance section and the anode side of which is connected with the other end (emitter side in the drawing) of the first semiconductor switch 22 of the balance section, the back current preventing diode 25, the cathode side of which is connected with one end (the collector side in the drawing) of the semiconductor switch 24 of the balance section and the anode side of which is connected with the other end (the emitter side in the drawing) of the second semiconductor switch 24 of the balance section, and the rector 26 of the balance section connected between the connecting point, which connects the first semiconductor switch 22 of the balance section and the second semiconductor switch 24 of the balance section, and the common line, compose a balance section which moves an electric charge between the first condenser 14, which is connected between P-voltage line and the common line, and the second condenser 15 connected between the common line and N-voltage line.
Reference numeral 27 is a battery operation switch, and reference numeral 28 is a battery which is an electric power supply for supplying electric power in the case of electric power failure. The negative electrode side of the battery 28 is connected with the common line, and the positive electrode side of the battery 28 is connected with the battery operation switch 27 and one end (collector side in the drawing) of the negative electrode side boosting section semiconductor switch 29 described later. Reference numeral 29 is a negative electrode side boosting section semiconductor switch, and reference numeral 30 is a negative electrode side boosting section diode, and reference numeral 31 is a negative electrode side boosting section reactor.
The battery 28, the negative electrode side boosting section semiconductor switch 29, one end (the collector side in the drawing) of which is connected with the positive electrode side of the battery 28 and the other end (the emitter side in the drawing) of which is connected with the negative electrode side boosting section reactor 31 and negative electrode side boosting section diode 30, the negative electrode side boosting section reactor 31 connected between the other end (the emitter side in the drawing) of the negative electrode side boosting section semiconductor switch 29 and the common line, and the negative electrode side boosting section diode 30 connected between the other end (the emitter side in the drawing) of the negative electrode side boosting section semiconductor switch 29 and N-voltage line, compose an N-side boosting section.
Reference numeral 32 is a voltage detector for detecting voltage of the first condenser 14 and for detecting voltage of the second condenser 15. Reference numeral 33b is a control circuit for controlling the switch 4 connected in parallel with the inrush electric current inhibiting resistor 3, the AC-electric-power-supply/battery changeover switch 5, the battery operation switch 27, the first semiconductor switch 11, the first semiconductor switch 16 of the inverter section, the second semiconductor switch 18 of the inverter section, the first semiconductor switch 22 of the balance section, the second semiconductor switch 24 of the balance section, and the negative electrode side boosting section semiconductor switch 29.
The conventional uniterruptible electric power supply operates as follows. The first condenser 14 and the second condenser 15 are electrically charged by the AC electric power supply 1 (in the case of normal operation) or the battery 28 (in the case of electric power failure). In the inverter section including the first semiconductor switch 16 of the inverter section, the diode 17, the second semiconductor switch 18 of the inverter section and the diode 19, DC electric power sent from the DC electric power supply, which is composed of the first condenser 14 and the second condenser 15, is converted into AC electric power. The thus converted AC electric power is supplied to the load 21.
FIGS. 5 and 6 are views for explaining operation of electrical charging conducted by the AC electric power supply 1 in the conventional uniterruptible electric power supply. In the views, reference numerals 1 and 3 to 15 are the same as those shown in FIG. 4. Therefore, explanations are omitted here.
Referring to FIGS. 4, 5 and 6, an electrically charging motion of the conventional uniterruptible electric power supply in the case of normal operation will be explained below.
In the case of normal operation conducted by the AC electric power supply 1, in the start of operation in which the AC-electric-power-supply/battery changeover switch 5 is set on the contact “a” side, the first condenser 14 and the second condenser 15 have not been electrically charged yet. Therefore, in order to inhibit an inrush electric current flowing into the first condenser 14 and the second condenser 15, the switch 4 is opened which is connected in parallel with the inrush electric current inhibiting resistor 3.
In the case where the AC electric power supply 1 generates a positive voltage, the first semiconductor switch 11 is turned on, and electric energy is stored in the reactor 6 by the route of the AC electric power supply 1→the inrush electric current inhibiting resistor 3 in the case of starting→the AC-electric-power-supply/battery changeover switch 5→the reactor 6→the diode 7 of the diode bridge→the first semiconductor switch 11→the diode 10 of the diode bridge→the AC electric power supply 1 as shown in FIG. 5A. Successively, the first semiconductor switch 11 is turned off and electric energy stored in the reactor 6 is charged into the first condenser 14 by the route of the reactor 6→the first diode 12 for preventing a back current→the first condenser 14→the AC electric power supply 1→the inrush electric current inhibiting resistor 3→the AC-electric-power-supply/battery changeover switch 5→the reactor 6, and the P-voltage line is formed with respect to the common line as shown in FIG. 5B.
In the case where the AC electric power supply 1 generates a negative voltage, the first semiconductor switch 11 is turned on, and electric energy is stored in the reactor 6 by the route of the AC electric power supply, →the diode 8 of the diode bridge→the first semiconductor switch 11→the diode 9 of the diode bridge→the reactor 6→the AC-electric-power-supply/battery changeover switch 5→the inrush electric current inhibiting resistor 3→the AC electric power supply 1 as shown in FIG. 6A. Successively, the first semiconductor switch 11 is turned off, and electric energy stored in the reactor 6 is charged into the second condenser 15 by the route of the reactor 6→the AC-electric-power-supply/battery changeover switch 5→the inrush electric current inhibiting resistor 3→the AC electric power supply 1→the second condenser 15→the second diode 13 for preventing a back current→the reactor 6, and the N-voltage line is formed with respect to the common line as shown in FIG. 6B.
When voltage of the first condenser 14 and voltage of the second condenser 15 are higher than the peak value of the AC electric power supply 1, for example, when voltage of the first condenser 14 and voltage of the second condenser 15 are 141 V in the case of operation of 100 V or when voltage of the first condenser 14 and voltage of the second condenser 15 are 180 V in the case of operation of 120 V, the switch 4 is short-circuited.
In the case of normal operation conducted by the AC electric power supply 1, after voltage of the first condenser 14 and voltage of the second condenser 15 have become higher than the peak value of the AC electric power supply 1, an electrically charging motion is executed by the route in which the above inrush electric current inhibiting resistor 3 is replaced with the switch 4.
In the case where the AC electric power supply 1 generates a positive voltage, the first semiconductor switch 11 is turned on, and electric energy is stored in the reactor 6 by the route of the AC electric power supply 1→the switch 4→the AC-electric-power-supply/battery changeover switch 5→the reactor 6→the diode 7 of the diode bridge→the first semiconductor switch 11→the diode 10 of the diode bridge→the AC electric power supply 1 as shown in FIG. 5A. Successively, the first semiconductor switch 11 is turned off, and electric energy stored in the reactor 6 is charged into the first condenser 14 by the route of the reactor 6→the first diode 12 for preventing a back current→the first condenser 14→the AC electric power supply 1→the switch 4→the AC-electric-power-supply/battery changeover switch 5→the reactor 6, and the P-voltage line is formed with respect to the common line as shown in FIG. 5B.
In the case where the AC electric power supply generates a negative voltage, the first semiconductor switch 11 is turned on, and electric energy is stored in the reactor 6 by the route of the AC electric power supply 1→the diode 8 of the diode bridge→the first semiconductor switch 11→the diode 9 of the diode bridge→the reactor 6→the AC-electric-power-supply/battery changeover switch 5→the switch 4→the AC electric power supply 1 as shown in FIG. 6A. Successively, the first semiconductor switch 11 is turned off, and electric energy stored in the reactor 6 is charged into the second condenser 15 by the route of the reactor 6→the AC-electric-power-supply/battery changeover switch 5→the switch 4→the AC electric power supply 1→the second condenser 15→the second diode 13 for preventing a back current→the reactor 6, and the N-voltage line is formed with respect to the common line as shown in FIG. 6B.
FIGS. 7 and 8 are views for explaining an electrically charging motion conducted by the battery 28 of the conventional uniterruptible electric power supply. In the views, reference numerals 5 to 7, 10 to 12, 14, 15 and 27 to 31 are the same as those shown in FIG. 4. Therefore, the explanations are omitted here.
Referring to FIGS. 4, 7 and 8, explanations will be made into the electrically charging motion conducted by the battery in the conventional uniterruptible electric power supply in the case of electric power failure.
In the case of electric power failure, the AC-electric-power-supply/battery changeover switch 5 is changed over to the contact “b” side, so that the battery operation switch 27 is short-circuited.
The first semiconductor switch 11 is turned on, and electric energy is stored in the reactor 6 by the route of the battery 28→the battery operation switch 27→the AC-electric-power-supply/battery changeover switch 5→the reactor 6→the diode 7 of the diode bridge→the first semiconductor switch 11→the diode 10 of the diode bridge→the battery 28 as shown in FIG. 7A. Successively, the first semiconductor switch 11 is turned off, and electric energy stored in the reactor 6 is charged into the first condenser 14 by the route of the reactor 6→the first diode 12 for preventing a back current→the first condenser 14→the battery 28→the battery operation switch 27→the AC-electric-power-supply/battery changeover switch 5→the reactor 6 as shown in FIG. 7B.
The negative electrode side boosting section semiconductor switch 29 is turned on, and electric energy is stored in the negative electrode side boosting section reactor 31 by the route of the battery 28→the negative electrode side boosting section semiconductor switch 29→the negative electrode side boosting section reactor 31→the battery 28 as shown in FIG. 8A. Successively, the negative electrode side boosting section semiconductor switch 29 is turned off, and electric energy stored in the negative electrode side boosting section reactor 31 is charged into the second condenser 15 by the route of the negative electrode side boosting section reactor 31→the second condenser 15→the negative electrode side boosting section diode 30→the negative electrode side boosting section reactor 31 as shown in FIG. 8B.
By using the voltage of the first condenser 14 and voltage of the second condenser 15 which are electrically charged in the above way, DC electric power is converted into AC electric power by the inverter section, so that AC electric power is supplied to the load 21. However, in the case where voltage of the first condenser 14 and voltage of the second condenser 15 are not balanced to each other by the unbalance of the load 21, electrical charges of the first condenser 14 and the second condenser 15 are moved by the action of the balance section which is composed of: the first semiconductor switch 22 of the balance section and the second semiconductor switch 24 of the balance section connected in series between P-voltage line and N-voltage line; and the balance section reactor 26 connected between the contact point, at which the first semiconductor switch 22 of the balance section is contacted with the second semiconductor switch 24 of the balance section, and the common line.
In the conventional uniterruptible electric power supply, at the time of start in which the first condenser 14 and the second condenser 15 are not electrically charged, in the case of connecting with the AC electric power supply 1, an inrush electric current flows in the first condenser 14 and the second condenser 15. In order to inhibit the intensity of the inrush electric current flowing in the first condenser 14 and the second condenser 15, it is necessary to use the inrush electric current inhibiting resistor 3 for inhibiting the inrush electric current flowing at the time of start. Since the inrush electric current inhibiting resistor 3 consumes a high intensity of electric power, the size of the resistor 3 is large. Further, the inrush electric current inhibiting resistor 3 consumes a high intensity of electric power and generates a large quantity of heat. Therefore, it is difficult to reduce the size of the uniterruptible electric power supply.
The present invention has been accomplished to solve the above conventional problems. It is an object to provide an uniterruptible electric power supply capable of inhibiting an excessively high intensity of inrush electric current at the time of start even when the inrush electric current inhibiting resistor 3 is not used.